code: def fill_hole(input_mask):
      h, w = input_mask.shape
      canvas = np.zeros((h + 2, w + 2), np.uint8)
      canvas[1 : h + 1, 1 : w + 1] = input_mask.copy()
  
      mask = np.zeros((h + 4, w + 4), np.uint8)
  
      cv2.floodFill(canvas, mask, (0, 0), 1)
      canvas = canvas[1 : h + 1, 1 : w + 1].astype(np.bool_)
  
      return ~canvas | input_mask
  
file_path: PaddleOCR/ppocr/modeling/heads/proposal_local_graph.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import cv2
  import numpy
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from lanms import merge_quadrangle_n9
  from ppocr.ext_op import RoIAlignRotated
  from .local_graph import euclidean_distance_matrix, feature_embedding, normalize_adjacent_matrix
label_desc: Use image node_id 1 for calling a global function with example usage: fill_hole(input_mask) and returns: unknown